Depending on the type of input types you're using on your form, you should be able to grab them using standard jQuery expressions.
Example:
// change forms[0] to the form you're trying to collect elements from... or remove it, if you need all of them
var input_elements = $("input, textarea", document.forms[0]);
Check out the documentation for jQuery expressions on their site for more info: http://docs.jquery.com/Core/jQuery#expressioncontext
